Field of the Invention
The invention relates generally to surround sound audio recording and, more specifically, to systems and methods for recording surround sound using a multichannel recording array.
Background Information
There are a number of existing “surround sound” systems which use digital or analogue equipment to record and reproduce sound. The goal of such systems is to recreate the sound environment. To recreate a sound environment, the surround sound system must be designed with an awareness of the human brain's ability to determine, within all three dimensions, where a given sound originates. The ear has two independent functions: first, to hear (auditory); second, to sense the motion of the listener or of an object in space identified by the listener (vestibular). The brain is able to recognize small differences in loudness and timing in sound waves as they reach both the left and right ears so as to exactly localize and follow a sound source in space. Realistic sound production must give the listener a sense of vestibular as well as auditory function, as the motion of the listener or object in space identified by the listener is necessary in the perception of reality.
In the past, recording in surround sound has been a cumbersome task. While there are microphone stands that support multiple microphones, they don't offer portability, nor do they offer a sonic advantage. Field recordists settle on small recording setups, usually consisting of a multi-capsule microphone, for portability. The problem is, there is no timing differences between the left and right channels of the array. A recordist may choose to use microphones spaced apart, utilizing timing differences to replicate a sound or space instead of relying solely on amplitude differences alone. The problem here is that the recordist must bring several microphone stands and cables along, and perhaps measuring equipment to place the microphones correctly within the array.
A typical surround sound environment consists of five to ten speakers placed around a room in several different configurations. In a movie theatre, for example, there may be three speakers behind the projection screen (left, center, and right), two speakers at the sides of the room (left-side and right-side) and two speakers at the rear of the room (left-surround and right surround). Each of these speakers is assigned its own specific channel. During the recording of the live sound sources for surround sound applications, the microphones are set up in a stationary positions at approximately the site at which the sound will be heard though the corresponding monitor speaker of the surround sound system.
Conventional techniques may utilize amplitude differences, and some even timing differences, but none of the techniques utilize frequency differences for recording surround sound. This leads to poor localization within the listening area. The human head filters out higher frequencies as they pass from one ear to another. None of these surround techniques take this into consideration, especially in conjunction with the other two localization factors. Thus, a need exists for a compact and low-cost multichannel array of microphones to record surround audio while taking all three factors into account.